It is known that polyethoxylated fatty alcohols and alkyl phenols are suitable for use as detergents and emulsifiers. In some applications, such as, for example, automatic dishwashers and washing machines, however, the strong foaming capacity of these compounds is a troublesome feature. Attempts have been made to counteract this undesirable property by adding suitable components, such as, for example, higher alcohols or block polymers of polypropylene glycol and ethylene oxide.
Another approach is to modify the hydrophilic portion of the tenside molecule. The replacement of the hydrogen of the terminal hydroxy group by a hydrophobic moiety, although accompanied by reduced water solubility of the resultant compound, produces a markedly reduced foaming tendency in comparison with that of the starting compound which is not "blocked". The complete absence of a terminal hydroxy group additionally causes the resultant compound to exhibit an improved stability in the presence of alkali hydroxides, silicates, or phosphates, i.e., compounds which are mixed with the mentioned tensides, for example, when used in powder-type dishwashing detergents. The literature discloses a plurality of suitable such blocking groups (N. Schoenfeldt, Surface Active Ethylene Oxide Adducts, Pergamon Press, Oxford [1969]: 659 et seq.). Propylene oxide and butylene oxide, in particular, are mentioned most frequently, but styrene oxide and benzyl chloride are also disclosed. Among the hydrophobic moieties enhancing alkali stability are, in particular, isopropyl and tert-butyl, obtainable by acid-catalyzed addition of propene (DAS [German Published Application] No. 2,544,569) or isobutene (DOS [German Unexamined Laid-Open Application] No. 2,556,499) to the end-positioned hydroxy function of the aforementioned tensides. U.S. Pat. No. 2,903,485 discloses the addition product of an epoxyoctane which is not exactly defined ("octylene oxide") to ethoxylated alkyl phenol in a molar ratio of 1:1 as being useful as a low-foaming detergent, especially for automatic dishwashers.